<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 插件： autoprefixer */
        input{color:red;}
    </style>   
</head>
<body>
    <input type="text" placeholder="用户名">
    
</body>
</html>  